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assert: add comments for diff algorithm

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It became hard to follow what was actually happening in the
algorithm. This adds comments to improve the situation.

PR-URL: https://github.com/nodejs/node/pull/23048
Refs: https://github.com/nodejs/node/issues/22763
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Shingo Inoue <leko.noor@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
This commit is contained in:
Ruben Bridgewater 2018-09-24 14:18:21 +02:00
parent 02c44a4894
commit eccc65919a
No known key found for this signature in database
GPG Key ID: F07496B3EB3C1762
1 changed files with 33 additions and 1 deletions
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34
lib/internal/assert.js
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@ -174,6 +174,9 @@ function createErrDiff(actual, expected, operator) {
// Only extra expected lines exist
const cur = i - lastPos;
if (actualLines.length < i + 1) {
// If the last diverging line is more than one line above and the
// current line is at least line three, add some of the former lines and
// also add dots to indicate skipped entries.
if (cur > 1 && i > 2) {
if (cur > 4) {
res += `\n${blue}...${white}`;
@ -185,11 +188,16 @@ function createErrDiff(actual, expected, operator) {
res += `\n ${expectedLines[i - 1]}`;
printedLines++;
}
// Mark the current line as the last diverging one.
lastPos = i;
// Add the expected line to the cache.
other += `\n${red}-${white} ${expectedLines[i]}`;
printedLines++;
// Only extra actual lines exist
} else if (expectedLines.length < i + 1) {
// If the last diverging line is more than one line above and the
// current line is at least line three, add some of the former lines and
// also add dots to indicate skipped entries.
if (cur > 1 && i > 2) {
if (cur > 4) {
res += `\n${blue}...${white}`;
@ -201,16 +209,30 @@ function createErrDiff(actual, expected, operator) {
res += `\n ${actualLines[i - 1]}`;
printedLines++;
}
// Mark the current line as the last diverging one.
lastPos = i;
// Add the actual line to the result.
res += `\n${green}+${white} ${actualLines[i]}`;
printedLines++;
// Lines diverge
} else {
const expectedLine = expectedLines[i];
let actualLine = actualLines[i];
// If the lines diverge, specifically check for lines that only diverge by
// a trailing comma. In that case it is actually identical and we should
// mark it as such.
let divergingLines = actualLine !== expectedLine &&
(!actualLine.endsWith(',') ||
actualLine.slice(0, -1) !== expectedLine);
// If the expected line has a trailing comma but is otherwise identical,
// add a comma at the end of the actual line. Otherwise the output could
// look weird as in:
//
// [
// 1 // No comma at the end!
// + 2
// ]
//
if (divergingLines &&
expectedLine.endsWith(',') &&
expectedLine.slice(0, -1) === actualLine) {
@ -218,6 +240,9 @@ function createErrDiff(actual, expected, operator) {
actualLine += ',';
}
if (divergingLines) {
// If the last diverging line is more than one line above and the
// current line is at least line three, add some of the former lines and
// also add dots to indicate skipped entries.
if (cur > 1 && i > 2) {
if (cur > 4) {
res += `\n${blue}...${white}`;
@ -229,14 +254,21 @@ function createErrDiff(actual, expected, operator) {
res += `\n ${actualLines[i - 1]}`;
printedLines++;
}
// Mark the current line as the last diverging one.
lastPos = i;
// Add the actual line to the result and cache the expected diverging
// line so consecutive diverging lines show up as +++--- and not +-+-+-.
res += `\n${green}+${white} ${actualLine}`;
other += `\n${red}-${white} ${expectedLine}`;
printedLines += 2;
// Lines are identical
} else {
// Add all cached information to the result before adding other things
// and reset the cache.
res += other;
other = '';
// If the last diverging line is exactly one line above or if it is the
// very first line, add the line to the result.
if (cur === 1 || i === 0) {
res += `\n ${actualLine}`;
printedLines++;
@ -246,7 +278,7 @@ function createErrDiff(actual, expected, operator) {
// Inspected object to big (Show ~20 rows max)
if (printedLines > 20 && i < maxLines - 2) {
return `${msg}${skippedMsg}\n${res}\n${blue}...${white}${other}\n` +
`${blue}...${white}`;
`${blue}...${white}`;
}
}